Washington — Steve Duarte worked in human resources for the same company for 19 years. But within months of returning from Iraq with his Marine Reserve unit in 2003 – his second military deployment in two years – he was told his job was ending in a week.

"There was that initial shock – and then the shock of 'What am I going to do?' " recalls Mr. Duarte of Littleton, Colo., whose expenses at the time included tuition for his son at the University of Denver.

As the wars in Iraq and Afghanistan grind on, tensions are mounting between the military's civilian volunteers, trying to step back into their professions, and employers, straining at times to cope with a growing cadre of workers who are away at war for months then expect to regain their former jobs. A 1994 law – the Uniformed Services Employment and Reemployment Rights Act (USERRA) – gives workers that right, along with promotions or other benefits they would have earned had they not been deployed. But with more than 600,000 reservists and guardsmen mobilized since 9/11, thousands have found their jobs gone or positions diminished when they returned.

Last week the Department of Justice said it was suing Wal-Mart, alleging that it failed to reinstate a cashier who was an Air Force reservist, and United Parcel Service, charging that it eliminated the job of another Air Force reservist while he was on active duty in Iraq in 2003.

The law is a ticklish issue for companies, experts say. On one hand, they don't want to do anything that makes them look unpatriotic. On the other, the long and sometimes repeated deployments of key personnel can complicate staffing.

"There continue to be companies that step forward and support guardsmen and reservists," says John Lowrie, an attorney with Ford and Harrison LLP, a labor-law firm that represents employers around the country. "There are other companies that do feel a strain, and it's difficult for them." Particularly under stress are airlines, police and fire departments, and other emergency-response services, whose key employees also tend to be in military reserve units, he adds.

"It can be a challenge for our smaller companies especially," says Jack Morton, manager of national security and emergency preparation at the US Chamber of Commerce. The chamber is working with the military to develop a predictable schedule for call-ups of the National Guard and reserve units.

Some 16,000 complaints filed

No one knows how big the problem is. Members of the reserve forces filed some 16,000 formal and informal complaints with the government from 2004 through 2006, says the Government Accountability Office (GAO), using the most recent data available. But that may underestimate the number who actually encounter rehiring problems, experts say.

Some aggrieved workers sue their employers on their own. Most apparently take no action at all. A GAO analysis of Defense Department surveys in 2004 and 2006 showed that some 70 percent of reservists who said they had problems getting rehired or promotions or raises did not seek redress.

One reason may be that the system is bureaucratic and can take months to decide a case.

Four government agencies handle complaints. The Defense Department's Employer Support of the Guard and Reserve (ESGR) offers informal mediation. The Labor Department tries to resolve formal complaints from service members without going to court. If they can't be resolved and are legitimate complaints, then the Justice Department or the Office of Special Counsel will take the case to court.

The system is actually working better than before as government agencies eventually geared up to handle all the complaints pouring in as a result of the largest activation of reserves in decades, according to the GAO. But it still criticized the process for delays and called for a single agency to oversee it.

The disputes are also more complex.

"In '03 and '04 our role was frequently more as a mediator and educator," says Mr. Lowrie, the lawyer who also serves as chairman of the Colorado ESGR. These days, more employees and employers are aware of USERRA's protections and cases are "slightly more a genuine dispute." The number of complaints ESGR ombudsmen receive has drifted down steadily from almost 6,000 in 2004 to a little more than 1,000 last year.

Justice Department suits are up slightly – rising from two to eight over the same period.

Stung by his sudden layoff notice from Agilent Technologies, Duarte called his commanding officer, Marine Col. George Aucoin, a New Orleans lawyer who knew of USERRA. When Duarte e-mailed company executives about the law, they said he was being laid off because of financial troubles and his job was not protected.

While sending out résumés, Duarte and Colonel Aucoin continued to research USERRA. The Labor and Defense departments said they couldn't represent him – for reasons that Duarte disputes.

In February 2004, Agilent posted an opening for a job very similar to Duarte's.

"That was kind of the nail in the coffin," says Duarte. He sued the next month.

A struggle – and $12,000 in costs

The case would ultimately cost Duarte $12,000. At the same time, he struggled to find another job. He and his wife lived off her salary, his severance from Agilent, and the pay from extra work he took on with his reserve unit. Finally, in April 2005, he went on active military duty "because I had to get back to work."

If it was hard to use USERRA to protect himself – a college-educated lieutenant colonel with years of work experience and savings – "there is no way a young [private first class] or lance corporal coming back is going to be able to fight this thing," he says.

A little over a year after filing his suit, the US district court in Colorado found in his favor, awarding him almost $400,000.

Agilent said in a statement that "although Agilent disagreed with the final outcome in this matter, we appreciated the opportunity ... to explain the reasons for the business decisions that were made.... Agilent remains committed to its employees who serve in the military."

"It's forced employers to take a very close look at allegations arising under USERRA and forced them to consider the ramifications associated with disputing a claim," says Lowrie.

Duarte has become an advocate of sorts on the issue, starting a website about his experience and recently testifying at a Senate hearing on USERRA. A year ago he finally found steady work, back in human resources with the city of Westminster, Colo.

It "was the first time my life got back to some semblance" of normal since 2003, says Duarte.